The question makes an excellent point; there is a free version with less storage space available and no Outlook sync as Clint mentioned. Another concern is that the free version limits a sender to 500 outbound email messages per day (compared to 3000 for the paid product) which could be a concern given the fact this company sends out announcements and invites to several hundred users at a time. Lastly, support seems a bit faster and more direct when using a subscription-based product compared to the free alternative.

Also, for those interested in learning the ins and outs of Google Apps, the free version is a great idea.